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Ultrasonic pulse shaping with optimal lag filters
Author(s) -
Fomitchev Max I.,
Grigorashvily Yuri E.,
Volkov Svyatoslav
Publication year - 1999
Publication title -
international journal of imaging systems and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.359
H-Index - 47
eISSN - 1098-1098
pISSN - 0899-9457
DOI - 10.1002/(sici)1098-1098(1999)10:5<397::aid-ima4>3.0.co;2-3
Subject(s) - waveform , filter (signal processing) , pulse shaping , ultrasonic sensor , acoustics , pulse (music) , raised cosine filter , signal (programming language) , low pass filter , computer science , optics , high pass filter , physics , telecommunications , laser , radar , detector , computer vision , programming language
Attempts to increase the resolution of ultrasound imaging apparata resulted in the desire for precise control over the shape of transmitted ultrasonic pulses. The shape of transmitted ultrasonic pulses can be controlled when a transducer is excited by a signal corresponding to a convolution filter. This article discusses a method of precise ultrasonic pulse shaping using lag filters. A lag filter f l (t) is a convolution filter calculated for a time‐shifted desired output waveform w(t): w(t) → w(t − l) . An optimal lag filter is selected by trying all possible values of lag l and selecting a filter with the best performance. The filter coefficients can be calculated using a Fourier transform or least‐squares criterion. The quality‐limiting factors of the pulse shaping are the length of the filter and the accuracy of the actual excitation signal. The improvement of the pulse‐shaping quality can be achieved by accounting for the amplifier transfer function or by accurate DAC‐values‐to‐voltage mapping. The analysis of the experimental results indicates that the developed ultrasonic pulse‐shaping technique provides a means for flexible control over the transmitted ultrasonic pulse waveform and frequency. The presented pulse‐shaping technique is specially developed for cost effective ultrasound imaging devices utilizing a simplified beamformer composed of a single pair of input/output amplifiers. © 1999 John Wiley & Sons, Inc. Int J Imaging Syst Technol 10, 397–403, 1999